In a blow molding machine, when molding a container with self-supporting legs or a container with a raised bottom, a bottom mold is assembled to a bottom portion of a blow cavity mold, the bottom mold is closed by a driving device such as a hydraulic cylinder, and a bottom shape such as the self-supporting legs or the raised bottom is formed at a bottom portion of the container.
In a blow molding process in which the blow cavity mold and the bottom mold are clamped together and blow air is introduced into an interior of a preform, a pressure receiving member which is fixed to the blow cavity mold is brought into engagement with the bottom mold or a bottom mold fixing plate so as to prevent the retracting of the bottom mold caused by blow pressure (Patent Document 1).
Here, in order to clamp the bottom mold to the blow cavity mold, it is necessary to bring the bottom mold or the bottom mold fixing plate into engagement with the pressure receiving member at the mold closing position of the bottom mold. In case the bottom mold, which is in a closed state, is positioned only at a substantially upper limit or lower limit driving position of the driving device, the positioning accuracy of the bottom mold becomes less reliable when the pressure receiving member is brought into engagement with the bottom mold (the bottom mold fixing plate).
Accordingly, in Patent Document 1, a stopper member is provided to a bottom mold or a bottom mold fixing plate to which the bottom mold is attached so as to regulate the position of the bottom mold relative to a blow cavity mold. According to this construction, when the blow cavity mold, in which blow molding is executed in an inverted state where a neck portion of the preform is oriented, for example, downwards, is opened, the bottom mold is moved downwards to close the mold. The stopper member is a plate-shaped member which is wider in width than the bottom plate. Thereafter, when the blow cavity mold is closed, an upper end face of the blow cavity mold is brought into abutment with the stopper member to thereby regulate the position of the bottom mold relative to the blow cavity mold. This allows the bottom mold to be positioned in the closed state. Additionally, by adjusting the thickness or parallelism of the stopper member, the closing position of the bottom mold or a positional relationship between cavity surfaces of the blow cavity mold and cavity surfaces of the bottom mold can be adjusted.
It is preferable that the blow cavity mold and the bottom mold are driven to be opened or closed in synchronism with each other. For example, the blow cavity mold and the bottom mold can be driven in synchronism with each other based on the output of a motor which is a single driving source (Patent Document 2).